JPH11135428A - Projection light alignment and projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner which can accurately monitor a variation in the light transmission factor of a projection optical system in a light exposure step to obtain a high exposure control accuracy. SOLUTION: Reference marks 114D, 114H and a window are previously formed on a reference mark member FM, and a part of a measurement system for measuring an amount of light passed through the window is previously provided in the interior of a sample base 21. When it is desired to perform alignment of a reticle R, reticle marks 113D and 113H on the reticle R are illuminated with exposing illumination light ILR and ILL, so that an alignment system 30 is used to measure positional shifts of images of the reticle marks 113D and 113H caused by a projection optical system PL relative to the reference marks 114D and 114H and simultaneously to measure an amount of illumination light passed through the projection optical system PL and window 105, thus detecting a variation in the light transmission factor of the system PL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithography process for manufacturing, for example, a semiconductor device, an image pickup device (CCD or the like), a liquid crystal display device, a thin film magnetic head, or the like. The present invention relates to a projection exposure method and a projection exposure apparatus used for transferring images onto a substrate.

[0002]

2. Description of the Related Art In order to cope with an improvement in the degree of integration and fineness of a semiconductor device or the like, a lithography process (typically, a resist coating process, an exposure process, and a resist development process) for manufacturing a semiconductor device is performed. In an exposure apparatus serving as a core, it is required to further improve resolution, transfer fidelity, and the like. In order to increase the resolution and the transfer fidelity as described above, it is necessary to control the exposure amount for exposing the resist applied on the wafer as the substrate at an appropriate exposure amount with high accuracy.

Conventionally, at a semiconductor device manufacturing site, a reduction projection optical system whose projection magnification from a reticle to a wafer is 1/5 times, mainly using i-line having a wavelength of 365 nm among illumination lines of a mercury lamp as illumination light for exposure. Step-and-
A repeat type reduction projection type exposure apparatus (stepper) has been frequently used. Recently, in order to prevent the projection field of view of the reduced projection optical system from becoming extremely large with the increase in the size (chip size) of the circuit device formed on the wafer, the projection optical system on the object plane side has to be prevented. By moving the wafer at a constant speed in the corresponding direction at the same speed ratio as the reduction magnification in the field of view on the image plane side of the projection optical system while moving the reticle in the field of view at a constant speed in a predetermined direction, the circuit pattern of the reticle is moved. Attention has also been focused on a step-and-scan type reduction projection type exposure apparatus that scans and exposes the entire image of each region on a wafer.

In the conventional exposure amount control, it is assumed that the transmittance of the projection optical system to the illumination light for exposure does not fluctuate in a short period of time. Using the transmittance of the projection optical system measured at a certain point in time, the exposure amount on the wafer surface is calculated from the amount of illumination light branched in the illumination optical system and the transmittance. In the case of a stepper, the exposure time is controlled so that the integrated value of the calculated exposure amount becomes a predetermined value. In the case of the step-and-scan method, the calculated exposure amount (illuminance) is constant. , The output of the light source, the scanning speed, and the like are controlled.

[0005]

Recently, a step-and-repeat method using an ultraviolet pulse light from an excimer laser light source as illumination light for exposure has been proposed in order to shorten the exposure wavelength and increase the resolution. And a step-and-scan projection exposure apparatus have been developed.
Projection exposure apparatuses using a 48 nm KrF excimer laser light source have begun to be put into production lines in earnest. Further, an ArF excimer laser light source which outputs a shorter ultraviolet pulse light having a wavelength of 200 nm or less and a wavelength of 193 nm has been developed, and this is expected as a light source for exposure in the future.

When this ArF excimer laser light source is used as an exposure light source, there are several oxygen absorption bands in the wavelength band in the spontaneous oscillation state of the ultraviolet pulse light.
It is desired to narrow the wavelength characteristic of the pulsed light to a wavelength that avoids those absorption bands. Furthermore, an environment is made such that oxygen is not contained as much as possible in the illumination light path from the exposure light source to the reticle and in the projection light path from the reticle to the wafer. It is desirable to replace with nitrogen gas or helium gas.
An example of a projection exposure apparatus using such an ArF excimer laser light source is disclosed in, for example, JP-A-6-260385,
It is disclosed in JP-A-6-260386.

At present, quartz (SiO ₂ ) is a practical optical glass material having a relatively high transmittance to ultraviolet pulse light (particularly, a wavelength of about 200 nm or less) from an excimer laser light source. Only two are known, fluorite (CaF ₂ ). Of course, other materials such as magnesium fluoride and lithium fluoride are also known. However, in order to use an optical glass material for a projection exposure apparatus, it is necessary to solve problems such as workability and durability. .

In this connection, the projection optical system mounted on the projection exposure apparatus is composed of a dioptric system (refraction system) and a combination of a refraction optical element (lens element) and a reflection optical element (particularly a concave mirror). Catadioptric systems (catadioptric systems) are also used. Regardless of which type of projection optical system is used, when a refractive optical element (transmitting optical element) is used as a part of the projection optical system, two types of glass materials, quartz and fluorite, are currently used as the refractive optical element. I have to use at least one of Further, regardless of whether the optical element is a refractive optical element or a reflective optical element, a multilayer film such as an anti-reflection film or a protective layer is deposited on the surface thereof, and the optical element is manufactured so that its performance as a single element is in a predetermined state. A particularly noteworthy performance here is how large the absolute value of the transmittance of the single lens element or the absolute value of the reflectance of the single reflective optical element can be obtained.

For example, in the case of a single lens element, an antireflection film or the like is generally coated on both the light incident surface and the light exit surface so as to maximize the transmittance. In a precise image forming optical system such as a projection optical system, a lens element used to satisfactorily correct various aberration characteristics requires 20 lens elements.
As many as 枚 30, and the transmittance of each lens element is slightly lower than 100%, the transmittance of the entire projection optical system becomes considerably small. Further, even in a projection optical system including several reflection optical elements, when the reflectance of each reflection optical element is low, the transmittance of the entire projection optical system is also low.

For example, if the projection optical system has 25 lens elements constituting an image forming optical path, and if the transmittance of each lens element is 96%, the transmittance ε of the entire projection optical system is about 36%. (≒ 0.96 ²⁵ × 100), which is considerably smaller. When the transmittance of the projection optical system is low, whether to increase the intensity (energy) of illumination light for exposing the circuit pattern image of the reticle onto the wafer or to use a more sensitive ultraviolet resist. If no measures are taken, the throughput will decrease due to the increase in the exposure time. Therefore, as a measure that can be realized on the projection exposure apparatus side, it is conceivable to prepare an excimer laser light source with higher output.

However, when a variety of exposure experiments were performed using a projection exposure apparatus having a relatively large field size using an excimer laser light source, it was found that irradiation with ultraviolet pulse light (KrF excimer laser light, ArF excimer laser light, etc.) An optical element in the projection optical system or a coating material of the optical element (for example, a thin film such as an anti-reflection film) during the time.
A new phenomenon has been discovered, such that the transmittance of the light-emitting element fluctuates dynamically. It has been found that this phenomenon can occur not only in the optical element in the projection optical system but also in the optical element in the illumination optical system that illuminates the reticle, and also in the reticle (quartz plate) itself.

Such a phenomenon occurs due to impurities contained in gas (air, nitrogen gas, etc.) existing in a space in a projection optical path or an illumination optical path, an adhesive for fixing an optical element to a lens barrel, and the like. (E.g., water molecules, hydrocarbon molecules, or any other substance that diffuses illumination light) generated from the organic substance molecules or the inner wall (anti-reflection painted surface, etc.) of the lens barrel of the optical element. It is thought to be caused by adhering to the surface or entering (floating) into the illumination light path. As a result, there arises a disadvantage that the transmittance of the projection optical system and the transmittance of the illumination optical system fluctuate relatively largely. In this case, if impurities adhere to the surface of the optical element, the transmittance (reflectance) decreases, but conversely, foreign matter on the surface of the optical element volatilizes due to irradiation with strong ultraviolet pulse light, and the transmittance (reflectance) of the optical element increases. (Reflectance) has also been observed. Whether the transmittance is reduced or improved by the irradiation of the ultraviolet pulse light as described above varies depending on the position where the optical member is disposed, the holding method, the state of gas in contact with the optical member, and the like.

For example, in a projection optical system having 25 lens elements and a transmittance ε of about 36%, assuming that the transmittance of a single lens element is uniformly reduced by 1%, the transmittance of the entire projection optical system is assumed. ε is about 27.7% (≒ 0.95 ²⁵ × 100)
Will decrease. Such a change in transmittance changes the exposure amount to be given on the wafer from an appropriate value, and deteriorates the transfer fidelity of a fine pattern having a design line width of about 0.25 to 0.18 μm transferred on the wafer. There is fear. In a conventional projection exposure apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-135723, the light intensity of illumination light is detected at a predetermined position in the optical path of an illumination optical system, and an appropriate light intensity is detected based on the detected light intensity. The intensity (energy per pulse) of the pulse light from the excimer laser light source is adjusted so as to obtain an exposure amount. For this reason, in the conventional projection exposure apparatus, the fluctuation of the transmittance of the illumination optical system and the projection optical system after the portion in the illumination optical path for detecting the intensity of the illumination light for controlling the exposure amount is not considered at all, and accurate projection exposure is performed. There was a risk that the exposure amount could not be controlled. Further, there is a possibility that the imaging characteristics of the projection optical system may change together with the transmittance fluctuation of the projection optical system.

Further, it has been found that when the irradiation of the projection optical system with the ultraviolet pulse light is stopped, the transmittance of the projection optical system gradually recovers (fluctuates).
In such a case, if the irradiation of the ultraviolet pulse light is started again and the exposure is restarted, accurate control of the exposure amount may be difficult because the transmittance of the projection optical system fluctuates. SUMMARY OF THE INVENTION In view of the foregoing, a first object of the present invention is to provide a projection exposure method capable of accurately monitoring the transmittance of a projection optical system during an exposure step, or the amount of variation thereof.

The present invention further provides a projection exposure method capable of preventing a deterioration in control accuracy of an exposure amount due to a change in illuminance (or a change in pulse energy) on a substrate caused by a change in transmittance of a projection optical system. As a second object. Another object of the present invention is to provide a projection exposure apparatus that can use such a projection exposure method.

[0016]

A projection exposure method according to the present invention irradiates a mask (R) with illumination light and exposes a substrate (W) with the illumination light via a projection optical system (PL). In the exposure method, the measurement pattern (114) placed on the stage (21, 22)
D, 114H), the photodetector (1) arranged in a predetermined positional relationship with the measurement pattern.
12) The irradiation area of the illumination light is limited to a predetermined area (16) including the light receiving unit (105) and the measurement pattern, and the projection optical system is used based on the output of the photodetector at the time of the irradiation. Is calculated.

According to the present invention, for example, the transmittance of the projection optical system can be measured in parallel with performing predetermined measurement using the measurement pattern. Then, based on the transmittance calculated as described above and the energy amount of the illumination light incident on the mask, the integrated light amount of the illumination light on the substrate is controlled to an appropriate value, so that the projection optical Even if the transmittance of the system fluctuates, deterioration of the control accuracy of the exposure amount is prevented.

Next, the first projection exposure apparatus according to the present invention provides an irradiation system (2 to 2) for irradiating the pattern formed on the mask (R) with an exposure energy beam having an ultraviolet wavelength.
5, 10, 11, 14), a projection optical system (PL) for projecting an image of the pattern of the mask onto the substrate (W), and a substrate stage (21, 22) for positioning the substrate.
And a plurality of alignment marks (113D, 113H) formed on a mask of an incident energy measuring system (8, 9) for measuring the amount of incident energy to the projection optical system. A plurality of corresponding reference marks (114D, 114H) and a window (105) for transmitting or reflecting the exposure energy beam are formed, and a reference mark member (FM) fixed on the substrate stage and the window thereof A detector (112) for detecting the exposure energy beam passing through the portion, and an alignment sensor (30) for detecting a positional shift amount between the alignment mark on the mask and the corresponding reference mark.
And an operation system (1b) for calculating the transmittance of the projection optical system (PL) for the exposure energy beam based on the measurement result of the incident energy amount measurement system and the detection result of the detector. It is.

According to the projection exposure apparatus of the present invention, the projection exposure method of the present invention can be used. That is, when the alignment mark is regarded as an example of the measurement pattern, for example, when exchanging a mask or exchanging a substrate, in order to align the mask with the substrate stage,
At substantially the same time as measuring the amount of displacement between the alignment mark on the mask and the reference mark on the reference mark member (FM) via the projection optical system using the alignment sensor (30), the detector (112) is used. ) detects the exposure energy beam quantity I _out passed through the projection optical system and the window portion (105) via, for detecting the exposure energy beam quantity I _in which enters the projection optical system at its entrance energy measurement system. Then, for example, by dividing the exposure energy beam quantity I _in which incident exposure energy beam quantity I _out which has passed through the projection optical system in the projection optical system, transmittance of the projection optical system is calculated. In this way, by calculating the transmittance every time a mask is replaced or each time a predetermined number of substrates (wafers) are replaced, the transmittance of the projection optical system can be increased at a high throughput without providing a transmittance measurement step. The amount of fluctuation can be monitored.

The amount of change in the transmittance of the projection optical system monitored in this manner can be used to set the amount of exposure to the substrate to a target value. Further, it can also be used to correct the measurement result of the reflectance of the substrate or to calibrate a sensor for measuring the transmittance of the projection optical system outside the exposure area of the projection optical system. Also, in the initial adjustment stage of the projection exposure apparatus, a change amount (history) of the transmittance of the projection optical system due to irradiation is measured in advance as a function of the irradiation time, and at the time of actual exposure, the projection optical system is adjusted based on the function. The transmittance may be corrected. At this time, based on the actual measured value of the transmittance of the projection optical system at the time of substrate exchange, etc., the function representing the variation of the transmittance is sequentially corrected, so that the variation of the transmittance of the projection optical system can be more accurately performed. The amount can be predicted.

The second projection exposure apparatus according to the present invention provides an irradiation system (2 to 2) for irradiating a pattern formed on a mask (R) with an exposure energy beam having an ultraviolet wavelength.
5, 10, 11, 14), a projection optical system (PL) for projecting an image of the pattern of the mask onto the substrate (W), and a substrate stage (21, 22) for positioning the substrate.
A plurality of alignment marks (113D, 113H) formed on the mask in the projection exposure apparatus having
A plurality of fiducial marks (114D, 114H) corresponding to
A window (105) for transmitting or reflecting the exposure energy beam, and a reference mark member (FM) fixed on the substrate stage, and a detector for detecting the exposure energy beam through the window (112)
An alignment sensor (30) for detecting an amount of displacement between the alignment mark on the mask and the corresponding reference mark, and an irradiation system from the irradiation system according to the detection result of the detector. And an exposure amount control system (1b, 1a) for controlling the exposure amount of the exposure energy beam applied to the substrate through the light emitting device.

According to the present invention, for example, when exchanging a mask, or when exchanging a mask when exchanging a substrate, the exposure energy beam passed through the projection optical system via the detector (112). Measure the amount. This makes it possible to monitor an accurate exposure amount on the substrate in consideration of the variation in the transmittance of the projection optical system. By controlling the exposure amount based on the result, the amount of exposure on the substrate caused by the variation in the transmittance of the projection optical system can be monitored. In this way, it is possible to prevent deterioration in the control accuracy of the exposure amount due to the illuminance fluctuation (or pulse energy fluctuation) in the above.

In these cases, for example, the exposure energy beam is pulsed light having a wavelength of 200 nm or less,
Further, a mask stage (17, 1) for moving the mask
8), and the mask and the substrate may be synchronously scanned with respect to the projection optical system via the substrate stage and the mask stage at the time of exposure. This means that the projection exposure apparatus uses a scanning exposure method such as a step-and-scan method.

Further, a third projection exposure apparatus according to the present invention provides an illumination optical system for irradiating a mask (R) with illumination light, and a projection optical system (PL) for projecting the illumination light on a substrate (W).
And a pattern detection system (30) that irradiates the illumination light to the measurement patterns (114D, 114H) and receives the illumination light via the projection optical system (PL). A first detector (105, 112) for receiving a part of the illumination light that has passed through the projection optical system when the measurement pattern is irradiated with the illumination light, and based on an output of the first detector To determine the transmittance of the projection optical system. The projection exposure method of the present invention is used by such a projection exposure apparatus.

At this time, a second detector (8, 9) for receiving a part of the illumination light which is incident on the mask through the illumination optical system, and the first detector and the second detector A computing unit (1) that determines the transmittance of the projection optical system based on the output
b), the transmittance of the projection optical system is easily and accurately calculated. A fourth projection exposure apparatus according to the present invention includes an illumination optical system that irradiates the mask (R) with illumination light, and a projection optical system (PL) that projects the illumination light onto the substrate (W). In a projection exposure apparatus, a stage (21, 22) disposed on the image plane side of the projection optical system, a measurement pattern (114D, 114H) provided on the stage, and the illumination light applied to the measurement pattern. In order to detect a part of the illumination light at the same time as the irradiation, the light receiving section (1) is provided within the irradiation area (16) of the illumination light irradiated on the measurement pattern on the stage.
05) are disposed. The projection exposure method of the present invention is also used by such a projection exposure apparatus.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a step-and-scan type scanning exposure type projection exposure apparatus using a catadioptric system as a projection optical system. FIG. 1 shows a schematic configuration of a projection exposure apparatus of the present embodiment. In FIG. 1, illumination light IL composed of ultraviolet pulse laser light emitted from an excimer laser light source 2 whose light emission state is controlled by an exposure control apparatus 1 is The light is deflected by the deflecting mirror 3 and reaches the first illumination system 4. In this example, the half width of the oscillation spectrum is 100 p as the excimer laser light source 2.
m ArF excimer laser (wavelength 193n)
m) Broadband laser light source is used. However, as the exposure light source, an F ₂ laser light source (wavelength: 157 nm), which is a halogen molecule laser, or a harmonic generation device of a YAG laser may be used. Further, a narrow band laser light source may be used in addition to the broad band laser light source. The narrow band laser light source is inferior to the broad band laser light source in output, but has an advantage that it is not necessary to perform achromatism.

The first illumination system 4 includes a beam expander,
It includes a light quantity variable mechanism, an illumination switching mechanism for switching the quantity of illumination light when the coherence factor (so-called σ value) of the illumination optical system is changed, a fly-eye lens, and the like. Then, the illumination light IL is applied to the exit surface of the first illumination system 4.
A secondary light source distributed in a plane is formed, and a switching revolver 5 for an illumination system aperture stop for variously switching illumination conditions is disposed on a surface on which the secondary light source is formed. On the side surface of the switching revolver 5, a normal circular aperture stop, an aperture stop for so-called deformed illumination composed of a plurality of apertures eccentric from the optical axis, an annular aperture stop, and a small σ value composed of a small circular aperture are provided. An aperture stop or the like is formed, and the switching device 6
By rotating the switching revolver 5 through the aperture, a desired illumination system aperture stop (σ stop) can be arranged on the exit surface of the first illumination system 4. Further, when the illumination system aperture stop is switched in such a manner, the illumination switching mechanism in the first illumination system 4 is switched by the switching device 6 so that the light amount becomes maximum.

The operation of the switching device 6 is the same as that of the exposure control device 1.
The operation of the exposure control apparatus 1 is controlled by a main controller 7 that controls the overall operation of the apparatus. The illumination light IL transmitted through the illumination system aperture stop set by the switching revolver 5 enters the beam splitter 8 having a large transmittance and a small reflectance, and
The illumination light reflected by is received by an integrator sensor 9 including a photoelectric detector such as a photodiode. The integrator sensor 9 corresponds to the second detector of the present invention. A detection signal obtained by photoelectrically converting illumination light by the integrator sensor 9 is supplied to the exposure control device 1. The relationship between the detection signal and the exposure amount on the wafer is measured and stored in advance, and the exposure control device 1 monitors the integrated exposure amount on the wafer from the detection signal. The detection signal is also used to normalize the output signals of various sensor systems using the illumination light IL for exposure. The incident energy of the illumination light IL with respect to the system PL is monitored.

Illumination light IL transmitted through beam splitter 8
Illuminates an illumination field stop system (reticle blind system) 11 via a second illumination system 10. This illumination field stop system 1
The arrangement surface 1 is conjugate with the entrance surface of the fly-eye lens in the first illumination system 4, and the illumination field stop system 11 is illuminated in an illumination area substantially similar to the cross-sectional shape of each lens element of the fly-eye lens. You. The illumination field stop system 11 is divided into a movable blind and a fixed blind, and the fixed blind is a field stop having a fixed rectangular opening. Are two pairs of movable blades. The fixed blind determines the shape of the illumination area on the reticle, and the movable blind gradually opens and closes the cover of the opening of the fixed blind at the start and end of scanning exposure. As a result, it is possible to prevent the area other than the original shot area on the wafer from being irradiated with the illumination light. Further, the fixed blind has a variable rectangular opening shape. That is, since the width of the opening in the short direction is changed in accordance with the position in the long direction, uneven illuminance on the wafer can be corrected.

The operation of the movable blind in the illumination field stop system 11 is controlled by a drive unit 12. When the stage control unit 13 performs synchronous scanning of a reticle and a wafer as described later, the stage control unit 13
Drives the movable blind in the scanning direction in synchronization with the driving device 12. The illumination light IL that has passed through the illumination field stop system 11 illuminates a rectangular illumination area 15 on the pattern surface (lower surface) of the reticle R with a uniform illumination distribution via a third illumination system 14. The arrangement surface of the fixed blind of the illumination field stop system 11 is conjugate with the pattern surface of the reticle R, and the shape of the illumination area 15 is defined by the opening of the fixed blind.

In the following, an X axis is taken perpendicular to the plane of FIG. 1 in a plane parallel to the pattern plane of the reticle R, and a Y axis is taken parallel to the plane of FIG. Take and explain. At this time, the illumination area 1 on the reticle R
Reference numeral 5 denotes a rectangular area elongated in the X direction, and the reticle R is scanned in the + Y direction or the −Y direction with respect to the illumination area 15 during scanning exposure. That is, the scanning direction is set in the Y direction.

The pattern in the illumination area 15 on the reticle R is projected through a telecentric projection optical system PL on both sides (or one side on the wafer side) with a projection magnification β (β is, for example, 1/4,
(1/5, etc.), and the image is projected onto a rectangular exposure area 16 on the surface of the wafer W coated with the photoresist. The wafer W is, for example, silicon or SOI (silicon oni).
nsulator) or the like.

The reticle R is held on a reticle stage 17, and the reticle stage 17 is mounted on a reticle support 18.
It is mounted on an upper guide extending in the Y direction via an air bearing. The reticle stage 17 can be moved at a constant speed in the Y direction on the reticle support base 18 by a linear motor, and has an adjustment mechanism that can adjust the position of the reticle R in the X direction, the Y direction, and the rotation direction (θ direction). . A moving mirror 19m fixed to the end of the reticle stage 17 and a laser interferometer (not shown except for the Y axis) 19 fixed to a column (not shown) are used to move the reticle stage 17 (reticle R) in the X and Y directions. The position in the direction is always measured with a resolution of about 0.001 μm, the rotation angle of the reticle stage 17 is also measured, and the measured value is supplied to the stage control device 13. The stage control device 13 responds to the supplied measured value. Thus, the operation of a linear motor or the like on the reticle support 18 is controlled.

On the other hand, the wafer W is held on a sample stage 21 via a wafer holder 20, the sample stage 21 is mounted on a wafer stage 22, and the wafer stage 22 is
It is mounted on the upper guide via an air bearing. The wafer stage 22 is configured to be able to move at a constant speed and step in the Y direction by a linear motor on the surface plate 23 and to move in the X direction. The wafer stage 22
A Z stage mechanism for moving the sample table 21 in a predetermined range in the Z direction and a tilt mechanism (leveling mechanism) for adjusting the tilt angle of the sample table 21 are incorporated therein.

Moving mirror 2 fixed to the side of sample stage 21
The position of the sample table 21 (wafer W) in the X and Y directions is always 0.001 μm by a laser interferometer (not shown except for the Y axis) 24 fixed to a 4 m and a column (not shown).
At the same time, the rotation angle of the sample table 21 is measured. The measured value is supplied to the stage control device 13, and the stage control device 13 controls the operation of the linear motor for driving the wafer stage 22 and the like according to the supplied measured value.

[0036] During the scanning exposure, the main control unit 7 of the exposure start to the stage control unit 13 from a command is sent, in the stage controller 13 in response thereto, the speed of the reticle R via the reticle stage 17 in the Y-direction V _R in synchronization with the scanning, it scans the wafer W via the wafer stage 22 at a velocity V _W in the Y direction. Reticle R to wafer W
The scanning speed V _W of the wafer _W is β
It is set to · V _R.

The projection optical system PL is held in an upper plate of a U-shaped column 25 planted on the surface plate 23. Then, a slit image or the like is projected obliquely to a plurality of measurement points on the surface of the wafer W on the side surface in the X direction of the projection optical system PL, and the position (focus position) in the Z direction at the plurality of measurement points is set. Output a plurality of corresponding focus signals,
Oblique incidence multi-point auto focus sensor (hereinafter, referred to as
An “AF sensor” 26 is disposed. A plurality of focus signals from the multi-point AF sensors 26 are supplied to a focus / tilt control device 27, and the focus / tilt control device 27 obtains a focus position and a tilt angle of the surface of the wafer W from the plurality of focus signals. ,
The obtained result is supplied to the stage control device 13.

In the stage controller 13, the focus position and the tilt angle supplied to the wafer stage 22 are adjusted so as to match the focus position and the tilt angle of the imaging plane of the projection optical system PL, which are obtained in advance. The Z stage mechanism and the tilt mechanism are driven by a servo system. Thereby, even during the scanning exposure, the exposure region 1 of the wafer W is
The surface in 6 is controlled by the autofocus method and the autoleveling method so as to match the image forming plane of the projection optical system PL.

Further, an off-axis type alignment sensor 2 for a wafer is provided on the side surface of the projection optical system PL in the + Y direction.
At the time of alignment, the alignment sensor 28 detects the position of an alignment wafer mark attached to each shot area of the wafer W, and a detection signal is supplied to the wafer alignment device 29. The measured value of the laser interferometer 24 is also supplied to the wafer alignment device 29,
Then, the coordinates of the wafer mark to be detected in the stage coordinate system (X, Y) are calculated from the detection signal and the measurement value of the laser interferometer 24 and supplied to the main controller 7. The stage coordinate system (X, Y) refers to a coordinate system determined based on the X and Y coordinates of the sample table 21 measured by the laser interferometer 24. The main controller 7 obtains array coordinates in the stage coordinate system (X, Y) of each shot area on the wafer W from the coordinates of the supplied wafer mark, and supplies the coordinates to the stage controller 13. Controls the position of the wafer stage 22 when performing scanning exposure on each shot area based on the supplied array coordinates.

Further, the reference mark member F
M is fixed, and various reference marks serving as a position reference of the alignment sensor, a reference reflection surface serving as a reference of the reflectance of the wafer W, and a projection optical system P are provided on the surface of the reference mark member FM.
An opening or the like for monitoring the irradiation energy of the illumination light IL irradiated onto the surface of the wafer W via the L is formed (details will be described later). A reticle alignment system 30 for detecting a light beam and the like reflected from the reference mark member FM side via the projection optical system PL is attached above the reticle R, and a detection signal of the alignment system 30 is transmitted to the reticle alignment device 31. Is supplied to

Next, the configuration of the projection optical system PL of this embodiment in FIG. 1 will be described in detail with reference to FIG. FIG. 2 is a cross-sectional view showing the projection optical system PL. In FIG.
The projection optical system PL is mechanically composed of four parts: a first objective section 41, an optical axis turning section 43, an optical axis deflecting section 46, and a second objective section 52. The concave mirror 45 is arranged in the optical axis turning part 43.

When a broadened laser beam is used as the illumination light IL as in this embodiment, the light amount can be increased even with the same power supply power, the throughput can be increased, and the coherency is reduced, and the adverse effect due to interference is reduced. There is an advantage of being reduced. However, when using illumination light in the ultraviolet region such as ArF excimer laser light as in this example, the glass material that can be used as a refractive lens in the projection optical system PL is limited to quartz, fluorite, or the like. It is difficult to design the system alone. Therefore, in this example, broadband achromatism is performed by using a reflective optical system and a refractive optical system that do not generate chromatic aberration like a concave mirror. However, the reflection optical system is generally a one-to-one (1: 1) optical system, and in the case of performing reduced projection such as 1/4 or 1/5 as in this example, the following is performed. However, a special device is required for the configuration.

That is, first, the first objective section 41 is disposed immediately below the reticle R, and the first objective section 41 is placed in the lens barrel 42 from the reticle R side through the lenses L1, L2, L2 through the lens frame.
L3 and L4 are fixed. And the lens barrel 4
2, a lens barrel 44 of the optical axis turning part 43 is disposed via a lens barrel 47 of the optical axis deflecting part 46, and the lenses L 11, L
, L20, L21, and the concave mirror 45 are fixed. The first objective section 41 and the optical axis turning section 43 are coaxial, and the optical axis is the optical axis AX1. The optical axis AX1 is perpendicular to the pattern surface of the reticle R.

At this time, in the lens barrel 47 of the optical axis deflecting section 46 between the lens barrel 42 and the lens barrel 44, a position decentered in the + Y direction from the optical axis AX1 in the + Y direction with respect to the optical axis AX1. A small mirror 48 having a reflective surface inclined at approximately 45 ° is arranged. In addition, the small mirror 48
The lenses L31 and L32 and the correction optical system 4 are sequentially arranged in the Y direction.
9 and a beam splitter 50. The optical axis AX2 of the optical axis deflecting unit 46 is orthogonal to the optical axis AX1,
The reflection surface of the beam splitter 50 is inclined at approximately 45 ° to the optical axis AX2 so as to be orthogonal to the reflection surface of the small mirror 48. The beam splitter 50 is a high-reflectance beam splitter having a transmittance of about 5% and a reflectivity of about 95%. For example, the beam splitter 50 detects a light beam reflected by the wafer W and transmitted through the beam splitter 50, thereby detecting the beam W The reflectance can be monitored. The correction optical system 49 includes a lens group that can finely move in a direction along the optical axis AX2 and that can finely adjust an inclination angle with respect to a plane perpendicular to the optical axis AX2.
The position and the tilt angle of the correction optical system 49 are determined by the imaging characteristic correction device 5.
1 is controlled. The operation of the imaging characteristic correction device 51 is controlled by the main control device 7 in FIG. The position where the correction optical system 49 is arranged is a position almost conjugate with the pattern surface of the reticle R, and can mainly correct distortion such as a magnification error.

Further, the optical axis AX2 is connected to the beam splitter 50.
The lens barrel 53 of the second objective section 52 is arranged so as to be in contact with the lens barrel 47 in the direction in which the beam splitter 50 is bent.
The lens L4 is inserted into the lens barrel 53 in order from the side via the lens frame.
, L52, L42, L43,...
The bottom surface of 2 faces the surface of wafer W. The optical axis AX3 of the second objective section 52 is parallel to the optical axis AX1 of the first objective section 41 and the optical axis turning section 43, and the optical axis deflecting section 46.
Is orthogonal to the optical axis AX2. In this case, the rectangular illumination area 15 on the reticle R by the illumination light IL is set at a position decentered in the −Y direction from the optical axis AX1, and the illumination light passing through the illumination area 15 (hereinafter, referred to as “imaging light flux”). ) Is the first
After passing through the lenses L1, L2,. The imaging light beam incident on the optical axis turning portion 43 is incident on the concave mirror 45 via the lenses L11, L12,..., L20, L21, and the imaging light beam reflected and collected by the concave mirror 45 is returned to the lenses L21, L20, …, L12,
After passing through L11, the light is deflected in the + Y direction by the small mirror 48 in the lens barrel 47 of the optical axis deflector 46.

In the optical axis deflecting section 46, the image forming light beam reflected by the small mirror 48 enters the beam splitter 50 via the lenses L 31 and L 32 and the correction optical system 49. At this time, the beam splitter 5 is
Near 0, an image (intermediate image) of substantially the same size as the pattern in the illumination area 15 on the reticle R is formed. Therefore, the first
The combined system including the objective unit 41 and the optical axis turning unit 43 is referred to as “1 × optical system”. The imaging light flux deflected in the −Z direction by the beam splitter 50 goes to the second objective unit 52,
In the second objective section 52, the image forming light beam is transmitted through the lens L4.
A reduced image of the pattern in the illumination area 15 on the reticle R is formed on the exposure area 16 on the wafer W via 1, L42,..., L51, L52. Therefore, the second objective unit 52 is also called a “reduction projection system”.

As described above, the illumination area 1 on the reticle R
The imaging light flux that has passed through the projection optical system 5 in the −Z direction is first objective section 41 and optical axis turning section 43 in the projection optical system PL of this example.
Is turned substantially in the + Z direction. The image forming light flux forms an intermediate image of substantially the same size as the pattern in the illumination area 15 in the process of being successively turned back in the substantially + Y direction and the −Z direction by the optical axis deflecting unit 46, and then the second objective unit A reduced image of the illumination area 15 is formed in the exposure area 16 on the wafer W via 52. With this configuration, in the projection optical system PL of this example, all the lenses L2 to L4, L11 to L11
L21, L31, L32, and L41 to L52 can be made axially symmetric, and almost all of the lenses are formed of quartz, and only three or four of the lenses are formed of fluorite. 1 which is the bandwidth of the banded illumination light IL
Achromatization can be performed with high accuracy within a range of about 00 pm.

The projection optical system PL of this embodiment is optically equal in size to the optical system including the first objective section 41 and the optical axis turning section 43, the optical axis deflecting section 46, and the second objective section. Part 52
The mechanical structure is such that a small mirror 48 is interposed between the lens L4 of the first objective unit 41 and the lens L11 of the optical axis turning unit 43. Therefore, if the lens L4, the small mirror 48, and the lens L11 are incorporated in the same lens barrel, it is necessary to incorporate the small mirror 48 and the beam splitter 50 in the optical axis deflecting unit 46 into separate lens barrels for adjustment. However,
If the small mirror 48 and the beam splitter 50 are incorporated in different lens barrels, there is a possibility that the orthogonality of the reflection surfaces of the two members may fluctuate. If the orthogonality between the two reflecting surfaces fluctuates, the imaging performance is degraded. In this example, the same-magnification imaging system is connected to the first objective unit 41 via the lens barrel 47 of the optical axis deflecting unit 46. The small mirror 4 is divided into an optical axis turning portion 43 and
8 and the beam splitter 50 are fixed in the lens barrel 47.

When assembling the projection optical system PL, the first objective section 41, the optical axis turning section 43, the optical axis deflecting section 46, and the second objective section 52 are separately assembled and adjusted in advance.
Then, the optical axis turning part 4 is inserted into the through hole of the upper plate of the column 25.
3 and the lower part of the lens barrel 53 of the second objective section 52 are inserted, and a washer is sandwiched between the flange 44a of the lens barrel 44 and the flange 53a of the lens barrel 53 and the upper plate of the column 25. 44a and 53a are temporarily fixed to the upper plate with screws. Next, the lens barrel 47 of the optical axis deflecting part 46 is placed on the upper ends of the lens barrels 44 and 53, and the flange 47a of the lens barrel 47 is mounted.
A washer is sandwiched between the upper end of the lens barrel 53 and the flange 53b, and the flange 47a is temporarily fixed on the flange 53b with a screw.

Then, a laser beam for adjustment is radiated from above the lens L 11 in the lens barrel 44 to the inside of the lens barrel 44, and the laser beam is applied to the lens L 5 at the lowermost end of the lens barrel 53.
A position (a position on the surface corresponding to the surface of the wafer W) that is ejected from the wafer 2 and is monitored, and the flanges 44a, 53a, and 4 are set so that the monitored position becomes a target position.
Adjusting the thickness of the washer at the bottom of the
7 and so on. Then, with the position of the laser beam reaching the target position, the flanges 44a, 53a,
47a by screwing, the optical axis turning portion 4
3. The second objective section 52 and the optical axis deflecting section 46 are fixed.
Finally, the first objective unit 4 is placed above the end of the lens barrel 47 in the -Y direction.
The first lens barrel 42 is moved, and the lens barrel 42 is mounted on the lens barrel 47 with a washer interposed between a flange (not shown) of the lens barrel 41 and a corresponding flange (not shown) of the lens barrel 47. Then, for example, a laser beam for adjustment is again irradiated from above the lens L1 of the lens barrel 42 to adjust the optical axis, and then the lens barrel 42 is screwed onto the lens barrel 47, whereby the projection optical system PL
Is completed in the projection exposure apparatus.

Further, in this embodiment, the center of gravity of the entire projection optical system PL is set outside the optical path of the imaging light beam in the projection optical system PL in consideration of the stability of the imaging characteristics against vibration and the balance of the projection optical system PL. 54 positions are set. That is, in FIG. 2, the center of gravity 54 of the projection optical system PL is
It is set at a position (inside the upper plate of the column 25) near the middle between the first and second objective sections 52 and slightly lower than the flange 44 a of the lens barrel 44 and the flange 53 a of the lens barrel 53.
As described above, by further setting the center of gravity 54 of the projection optical system PL near the flanges 44a and 53a, the projection optical system PL has a structure that is more resistant to vibration and has high rigidity.

As described above, the projection optical system PL of this embodiment
Inside the optical axis deflecting unit 46 and the beam splitter 50
, There is an intermediate image plane conjugate to the pattern surface of the reticle R, and a correction optical system 49 is arranged near this intermediate image plane. The reticle R projected on the wafer W by, for example, finely moving a lens group as the correction optical system 49 in the direction of the optical axis AX2 or adjusting the inclination angle of the lens group with respect to a plane perpendicular to the optical axis AX2. And the imaging characteristics such as distortion and the projection magnification of the reduced image. On the other hand, conventionally, such an imaging characteristic correcting mechanism is provided almost immediately below the reticle R. According to the present example, there is no imaging characteristic correction mechanism immediately below the reticle R, and there is no restriction on the mechanism. Therefore, there is an advantage that the rigidity of the reticle support 18 in FIG. 1 can be increased in design. The correction optical system 4
By providing an optical system capable of fine movement similar to 9 in the optical axis turning section 43 or the second objective section 52, it is also possible to correct aberrations (astigmatism, coma, etc.) of the projected image and to correct the field curvature. Become. Further, it is also possible to correct a higher-order magnification error by using these combinations.

Next, referring to FIG. 3, reticle R of FIG.
The positional relationship between the upper illumination area 15 and the exposure area 16 on the wafer W will be described. FIG. 3A shows the reticle R of FIG.
The upper illumination area 15 is shown, and in FIG. 3A, in the circular effective illumination visual field 41a of the first objective section 41 of the projection optical system PL in FIG. A rectangular illumination area 15 that is long in the X direction is set at a position deviated from. The short side direction (Y direction) of the illumination area 15 is the scanning direction of the reticle R. In FIG. 2, in an equal-magnification optical system including a first objective section 41 and an optical axis turning section 43, an image forming light beam passing through the illumination area 15 on the reticle R is turned by the concave mirror 45 and guided to the small mirror 48. Therefore, the illumination area 15 needs to be decentered with respect to the optical axis AX1.

On the other hand, FIG. 3B shows an exposure region 16 (a region conjugate with the illumination region 15) on the wafer W in FIG. 2, and in FIG. 2 circular effective exposure field 52 of the objective section 52 (reduction projection system)
A rectangular exposure area 16 long in the X direction is set at a position slightly deviated in the + Y direction with respect to the optical axis AX3 within a.

On the other hand, FIG. 3C shows the state shown in FIG.
Similarly, the rectangular illumination area 15 is set at a position slightly deviated in the −Y direction with respect to the optical axis AX1 in the circular effective illumination visual field 41a. Further, FIG.
The effective exposure field 52aA of the second objective section obtained by deforming the second objective section 52 of FIG.
A rectangular exposure area 16A (a conjugate area with the illumination area 15 in FIG. 3C) is set in the X direction with the optical axis AX3A of aA as a center. That is, as shown in FIG. 3D, by changing the configuration of the second objective section 52 (reduction projection system), which is the last stage of the projection optical system PL, the exposure area 16A on the wafer W becomes an effective exposure field. It can be set to a region around the optical axis of 52aA. FIG. 3 (b) and FIG.
(D) is selected depending on the easiness of design for removing aberration of the projection optical system PL. FIG. 3 (b) is easy to design, and FIG. 3 (d) is the second objective unit. (Reduced projection system)
There is an advantage that the lens diameter can be slightly reduced.

Next, the configuration of the off-axis type alignment sensor 28 of FIG. 1 will be described in detail with reference to FIG. FIG. 4 shows the appearance of the projection optical system PL of FIG.
As shown in FIG. 4, the projection optical system PL includes a first objective section 41, an optical axis deflecting section 46, an optical axis turning section 43, and a second
It is divided into the objective part 52, and it is necessary to design such that it is not distorted by disturbance such as vibration or heat. Therefore, the rigidity of the column 25 on which the flanges 44a and 53a are placed,
In particular, high rigidity is required for the portion 25a of the column 25 between the optical axis turning portion 43 and the second objective portion 52. In order to secure such rigidity, the alignment sensor 28 for detecting the position of the wafer mark WM as an alignment mark on the wafer W is provided on the side surface of the second objective section 52 and in a portion where the high rigidity is required. 25a
, Ie, on the side surface of the second objective section 52 in the + Y direction. In the column 25, a portion 25b facing the side surface portion in the + Y direction and the side surface portions in the + X direction and the -X direction of the second objective portion 52 is a portion 2 having high rigidity.
The thickness of the thin portion 25b is smaller than that of the thin portion 25a, and the alignment sensor 28 is disposed at the bottom of the thin portion 25b. With this arrangement, the reticle R
Also, when the wafer W is scanned in the direction of the arrow (Y direction), the first objective section 41, the optical axis deflecting section 46, the optical axis turning section 43, and the second objective section 52 are formed as an integral projection optical system PL. The projection optical system PL is supported and high rigidity is obtained.

In the off-axis type alignment sensor 28 shown in FIG. 4, during alignment, a broadband (white) alignment light AL having low photosensitivity to the photoresist on the wafer W emitted from a halogen lamp or the like (not shown) is emitted. Is guided into the lens barrel 61 of the alignment sensor 28 via the light guide 62. In the lens barrel 61, the alignment light AL passes through the half mirror 64 via the condenser lens 63, and then includes the wafer mark WM on the wafer W via the first objective lens 65 and the prism type deflection mirror 66. A predetermined range of the observation field is illuminated. The reflected light from the wafer mark WM is reflected by the half mirror 64 via the deflection mirror 66 and the first objective lens 65,
An image of the wafer mark WM is formed on the index plate 68 by the second objective lens 67. On the index plate 68, an index mark serving as a reference for detecting the position of the wafer mark WM is formed.

The light beam transmitted through the index plate 68 is transmitted to the first relay lens 69, the deflecting mirror 70, and the second relay lens 7.
After 1, images of the wafer mark WM and the index mark are re-formed on the image sensor 72 formed of a two-dimensional CCD. Here, the wafer mark WM is, for example, an uneven Y-axis lattice mark arranged at a predetermined pitch in the Y direction.
2 are supplied to the wafer alignment device 29 of FIG. In the wafer alignment device 29, the amount of displacement of the wafer mark WM in the Y direction with respect to the index mark on the index plate 68 is calculated based on the imaging signal, and the amount of displacement is measured by the laser interferometer 24 in FIG. The Y coordinate of the wafer mark WM in the stage coordinate system (X, Y) is calculated by adding
To supply. An X-axis wafer mark having a shape obtained by rotating the wafer mark WM by 90 ° is also attached to the shot area on the wafer W, and the X coordinate of the X-axis wafer mark in the stage coordinate system (X, Y) is also changed. Alignment sensor 2
8 detected. As described above, the alignment of the wafer W is performed by detecting the coordinates of the wafer mark attached to the predetermined shot area on the wafer W via the alignment sensor 28.

In order to perform the measurement by the alignment sensor 28 with high accuracy, the detection center of the alignment sensor 28 (the center of the projected image of the index mark on the wafer W)
It is desirable to minimize the distance (baseline amount) between the image and the center of the projected image of the pattern of the reticle R by the projection optical system PL (the center of the exposure area 16). For this purpose, the alignment sensor 28 is arranged as close as possible to the second objective section 52 of the projection optical system PL. Also,
The baseline amount can be measured using the reference mark member FM in FIG.

However, as an apparatus that needs to be arranged close to the second objective section 52, in addition to the off-axis type alignment sensor 28, it is necessary to detect the focus position and the inclination angle of the surface of the wafer W. There is also a multi-point AF sensor 26 shown in FIG. Therefore, in this example, in order to prevent mechanical interference between the alignment sensor 28 and the AF sensor 26, the AF sensor 26 is
Is disposed on the side surface in the ± X direction with respect to the second objective unit 52 so as to be orthogonal to.

FIG. 5 shows an arrangement state of the AF sensor 26. FIG. 5 is a sectional view taken along a plane (XZ plane) passing through the optical axis AX3 of the second objective section 52 in FIG. 4 and perpendicular to the Y axis. However, for convenience of explanation, the upper half of FIG. 5 is a left side view of the reticle and the first objective unit 41 of FIG. In FIG. 5, the AF sensor 26 is divided into an irradiation optical system 26a and a condensing optical system 26b, and the irradiation optical system 26a and the condensing optical system 26b are respectively connected to the -X direction and + of the second objective unit 52.
It is arranged on the side surface in the X direction and at the bottom of the thinner portion 25b as compared with the thicker, thicker portion 25a of the column 25 shown in FIG.

First, in the irradiation optical system 26 a, substantially white illumination light having a low photosensitivity to the photoresist from a halogen lamp or the like (not shown) is guided to the side surface of the second objective section 52 via the light guide 81. The illumination light passes through a mirror 82 and a condenser lens 83 and passes through a multi-slit plate 8 in which a plurality of slit-shaped openings are formed in a predetermined arrangement.
Light 4 The illumination light that has passed through each slit-shaped opening of the multi-slit plate 84 is
6 and the optical axis AX3 on the wafer W via the lens 87.
, A plurality of slit images (a single slit image 88 is representatively shown in FIG. 5) which are conjugate images of the plurality of slit-shaped openings are projected. The areas where these slit images are projected are within the rectangular exposure area 16 on the wafer W shown in FIG. 1 and the pre-read area on the near side in the scanning direction with respect to the exposure area 16.

The reflected light from the plurality of slit images on the wafer W enters the condenser optical system 26b. Condensing optical system 2
6b, the reflected light is transmitted through a lens 89 and a mirror 90.
After passing through the lens 91 and the multi-slit plate 92, the plurality of slit images (88 and the like) are re-imaged on the multi-slit plate 92 in which a plurality of slit-shaped openings are formed corresponding to the multi-slit plate 84. In addition, on the back surface of the multi-slit plate 92, a photoelectric detector 93 in which photoelectric conversion elements such as photodiodes that independently receive reflected light passing through each slit-shaped opening of the multi-slit plate 92 are arranged, A photoelectric conversion signal from each photoelectric conversion element of the photoelectric detector 93 (hereinafter, referred to as a photoelectric conversion signal)
(Referred to as a “focus signal”) is supplied to the focus / tilt control device 27.

In this case, due to the vibration of the vibration mirror 86, the slit image re-imaged on the multi-slit plate 92 vibrates in the short side direction on the corresponding slit-like opening, and the focus position ( When the position in the Z direction changes, the center of vibration of the slit image and the center of the corresponding slit-shaped opening are shifted laterally. Therefore, the focus signal, which is a photoelectric conversion signal of the reflected light passing through each slit-shaped opening, is synchronously rectified by the drive signal of the vibrating mirror 86 in the focus / tilt control device 27, thereby obtaining each slit image ( 88 etc.), a signal corresponding to the change amount of the focus position at the projection position is obtained. Further, the calibration of the AF sensor 26 is performed so that the synchronous rectification signal of the focus signal becomes 0 when the surface of the wafer W matches the image plane of the projection optical system PL in advance. Therefore, the focus / tilt control device 27
Then, from these synchronous rectification signals, the average value of the focus position in the exposure region 16 on the wafer W and the pre-read region with respect to the exposure region 16 and the inclination angle can be obtained. The information on the average value of the focus positions and the information on the tilt angle are supplied to the stage control device 13 via the main control device 7 in almost real time. Auto-focusing and auto-leveling are performed so that the exposure area 16 of FIG.

Next, in FIG. 1, the laser interferometer and the movable mirror on the wafer side and the movable mirror which are actually arranged two-dimensionally are one laser interferometer 24 and one movable mirror 24m, respectively.
It is represented by Therefore, an example of a specific arrangement of the laser interferometer and the moving mirror on the wafer side of the present embodiment will be described with reference to FIGS. FIG. 6 is a plan view of the sample stage 21 on which the wafer W of FIG. 1 is mounted. For convenience of description in FIG. 6, the outer shape of the second objective section 52 of the projection optical system PL of FIG. Observation field 28a of alignment sensor 28
And the external shape of the first objective section 41 and the optical axis turning section 43 and the reticle R are shown in an accurate positional relationship. FIG. 6 shows a state where the optical axis AX3 of the second objective unit 52 is on the reference mark member FM on the sample table 21.

In this example, as shown in FIG. 2, the column 25 between the first objective section 41 and the optical axis turning section 43 of the projection optical system PL and the second objective section 52 is provided to increase rigidity. It has a strong structure, and it is difficult to arrange a laser interferometer between them. Furthermore, even if a laser interferometer can be placed between them, there is not enough space for air conditioning by downflow along the optical axis of the laser interferometer, and the laser interferometer is easily affected by air fluctuation. Will be.

In order to avoid the influence of air fluctuation, in this example, as shown in FIG. 6, the laser interferometer is connected to the optical axis turning section 43 with respect to the second objective section 52 of the projection optical system PL.
, Ie, in the + Y direction and the −X direction with respect to the second objective section 52. In FIG. 6, + Y of the sample stage 21 is shown.
Mirror 24 having a reflecting surface perpendicular to the Y axis on the side surface in the direction
mY is fixed, and a moving mirror 24mX having a reflecting surface orthogonal to the reflecting surface of the moving mirror 24mY (perpendicular to the X axis) is fixed to the side surface of the sample table 21 in the −X direction. A Y-axis laser interferometer 24Y is arranged so as to face the Y-axis movable mirror 24mY, and a three-axis laser beam is emitted from the laser interferometer 24Y to the movable mirror 24mY in parallel with the Y-axis. In FIG. 6, two-axis laser beams LBY1, LBY arranged at a predetermined interval in the X direction among the three-axis laser beams are shown.
BY2, these two-axis laser beams LBY1, LBY
BY2 passes through a position symmetrical with respect to a straight line parallel to the Y axis passing through the optical axis AX3 of the second objective section 52 and the center of the observation field 28a of the alignment sensor 28.

FIG. 7A shows that the sample stage 21 of FIG.
FIG. 7 is a side view as viewed in the X direction. As shown in FIG. 7A, the Z-axis laser beams LBY1 and LBY2 are
The laser beam LBY3 of the third axis is emitted from the laser interferometer 24Y to the moving mirror 24mY in parallel with the Y axis at predetermined intervals in the direction. As shown in FIG. 7B, the laser beam LBY3 is a biaxial laser beam LBY in the X direction.
1 and LBY2. In the laser interferometer 24Y, the three-axis laser beams LBY1, LB
Y coordinates Y1, Y corresponding to Y2, LBY3, respectively
2 and Y3 are constantly detected with a resolution of about 0.001 μm and output to the stage control device 13. The stage controller 13 obtains, for example, an average value and a difference between the two Y coordinates Y1 and Y2 as the Y coordinate and the rotation angle (yaw) of the sample table 21, respectively. At the time of measuring the rotation angle, the bending of the movable mirror 24mY is also corrected.

In FIG. 6, the X-axis movable mirror 24m
An X-axis laser interferometer 24X is arranged so as to face X, and a three-axis laser beam is emitted from the laser interferometer 24X to the movable mirror 24mX in parallel with the X-axis. In FIG.
Among them, there are shown two-axis laser beams LBX1 and LBX2 arranged at predetermined intervals in the Y direction, and these laser beams LBX1 and LBX2 are respectively provided in the second objective section 52.
Pass through an optical path parallel to the X-axis through the optical axis AX3 of the above and an optical path parallel to the X-axis through the center of the observation field 28a of the alignment sensor 28.

Also, as in FIGS. 7 (a) and 7 (b),
The laser beams on the third axis are arranged at predetermined intervals in the Z direction with respect to the laser beams LBX1 and LBX2 on the third axis.
The moving mirror 24mX is irradiated from X in parallel with the X axis.
In the laser interferometer 24X, the two-axis laser beam LBX1,
The X-coordinates X1 and X2 corresponding to each of the LBXs 2 and the X-coordinate X3 corresponding to the remaining one axis are constantly detected with a resolution of about 0.001 μm, and output to the stage controller 13. The stage controller 13 sets the X coordinate X1 corresponding to the optical axis AX3 at the time of exposure to the wafer W to the sample stage 21.
During the alignment, the X coordinate X2 corresponding to the center of the observation visual field 28a is set as the X coordinate of the sample table 21.
As a result, in each of the exposure and the alignment, the so-called Abbe error caused by the displacement between the measurement target position and the measurement axis becomes almost zero, and the position can be detected with high accuracy. In addition, like the moving mirror 24mY of the Y axis,
The bending of the movable mirror 24mX can be corrected based on the two X coordinates X1 and X2.

As a result, in this example, as shown in FIG.
Laser interferometers 24Y and 24X are arranged in the + Y direction and the -X direction with respect to the sample table 21, respectively.
1, the optical axis turning portion 43 along the -Y direction,
A projection optical system PL including an objective section 52 and the like is arranged, and is located on the + X direction side (the laser interferometer 24) with respect to the sample table 21.
(A direction symmetrical with X). Therefore, in this example, the sample table 21 is located on the + X direction side,
A wafer transfer system including a wafer loader WL for loading and unloading a wafer onto and from the sample stage 21 is arranged.

With this configuration, the laser interferometer 24X,
Air conditioning that causes a downflow to the optical path of the laser beam from 24Y can be performed. Specifically, for example, air or the like having a uniform velocity distribution and a uniform temperature distribution is applied from above the laser beams LBY1, LBY2, LBX1, and LBX2 to the floor surface on which the projection exposure apparatus is installed. Downflow air conditioning is performed by collecting the air and the like on the floor surface. Thereby, the laser interferometer 2
In 4X and 24Y, there is an advantage that the influence of air fluctuation on the optical path of the laser beam is reduced and the measurement accuracy of the position, the rotation angle, and the like of the sample table 21 is improved.

In FIG. 7A, the sample stage 21 is formed of ceramics and has a movable mirror 24 mY (24 mX
Is also formed of ceramics of the same material as the sample table 21. The movable mirror 24mY is fixed to a side surface of the sample table 21 via fixing screws (not shown).
However, the wafer W is placed on the sample stage 21 by the wafer holder 20.
, The position of the wafer W and the position of the optical axis of the laser beams LBY1 and LBY2 from the laser interferometer 24Y are shifted in the Z direction. Therefore, when pitching or the like occurs on the sample stage 21, the Y coordinate measured by the laser interferometer 24Y due to the so-called Abbe error and the sample stage 2
1 (more precisely, the wafer W) has a displacement amount ΔY between the actual Y coordinate. Therefore, in this example, the average value (Y1 + Y2) / 2 of the Y coordinate measured by the laser beams LBY1 and LBY2 is used by using the laser beam LBY3 passing through the position shifted in the Z direction with respect to the laser beams LBY1 and LBY2. And the Y-coordinate Y3 measured by the laser beam LBY3, the inclination angle Δθ of the sample table 21 around the X axis is calculated. And the inclination angle Δθ
, The average value of the Y coordinate measured by the laser beams LBY1 and LBY2 is corrected, thereby correcting the Abbe error caused by the difference between the height of the wafer W and the heights of the laser beams LBY1 and LBY2.

Similarly, also for the X-axis laser interferometer 24X, the Abbe error mixed in the measured values of the laser beams LBX1 and LBX2 is corrected by using the measured value of the laser beam on the third axis. . By adopting the method of attaching the movable mirrors 24mY and 24mX to the side surfaces of the sample table 21 as described above, as shown in FIG.
The space on 4 mY and 24 mX can be used effectively, for example, by arranging the end of the wafer holder 20. As a result, the entire sample stage 21 can be reduced in size and weight, so that controllability during scanning and positioning of the wafer W is improved.

Further, complicated processing of ceramics requires time, and the production cost is extremely high. On the other hand, in this example, the movable mirrors 24mY and 24mX which require surface accuracy
And the sample table 21 are manufactured separately while being made of the same material, and then combined to simplify the shape of each part,
Overall, manufacturing costs are reduced. If the temperature control is difficult, the rigidity is reduced but glass ceramics (for example, Zerodur (trade name, manufactured by Shot) can be used)
A material having a small coefficient of linear expansion such as the above may be used instead of ceramics.

Next, with reference to FIGS. 8 and 9, the configuration of the alignment system 30 on the reticle R side, the alignment marks (reticle marks) formed on the reticle R, and the corresponding reference marks in the present embodiment, and An example of the alignment operation of the reticle R using the method will be described. FIG.
FIG. 9 is a side view of a member from the third illumination system 14 and the alignment system 30 to the wafer stage 22 in FIG. 1 when viewed in the Y direction. In FIG. Are formed, for example, four pairs of reticle marks each composed of a cross-shaped two-dimensional mark. Then, the reference mark member FM on the sample table 21
Are formed with four pairs of reticle marks in an array in which the four pairs of reticle marks are reduced by the projection magnification. The surface of the reference mark member FM is set at the same height as the surface of the wafer W. I have. The reference mark of this example is, for example, a reflective cross-shaped two-dimensional pattern formed on a light transmissive substrate.

FIG. 9 is an enlarged plan view showing a state in which the reference mark member FM in FIG. 8 and a part of the projection image RP of the reticle R are superimposed.
On M, a first pair of fiducial marks 1 at predetermined intervals in the Y direction
14A, 114E, a second pair of fiducial marks 114B,
114F, third pair of fiducial marks 114C, 114
G and a fourth pair of reference marks 114D and 114H are formed. In FIG. 9, an image PAP of the pattern area is projected onto the center of the projected image RP of the reticle R, and the first image PAP is provided on both sides of this image PAP at predetermined intervals in the Y direction.
Pair of reticle mark images 113AP and 113EP, second pair of reticle mark images 113BP and 113FP, third
Pair of reticle mark images 113CP and 113GP, and a fourth pair of reticle mark images 113DP and 113H.
P is projected. 8, a pair of reference marks 114D and 114H and a reticle mark image 113D of FIG.
Reticle mark 113D, 1 corresponding to P, 113HP
13H has appeared.

When aligning the reticle R in this embodiment, first, as shown in FIG. 9, the reference marks 114D, 114 on the reference mark member FM are placed in the rectangular exposure area 16.
H is set, and the reticle R is positioned so that the reticle mark images 113DP and 113HP substantially overlap the reference marks 114D and 114H. In this state, as shown in FIG. 8, a pair of half prisms 101R, 101L of the alignment system 30 is inserted into the optical path of the illumination light ILR, ILL from the third illumination system 14 toward the reticle R. During normal exposure, the half prisms 101R, 101R
L is retracted outside the optical path.

Then, one of the illumination lights ILR from the third illumination system 14 is transmitted through the half prism 101R and applied to the reticle mark 113D on the reticle R, and the illumination light reflected by the reticle mark 113D is applied to the half prism 101R. Return to 101R. Further, the illumination light ILR transmitted around the reticle mark 113D illuminates the reference mark 114D on the reference mark member FM via the projection optical system PL, and the reflected light from the reference mark 114D is reflected by the projection optical system PL and The light returns to the half prism 101R via the reticle R. The reflected light from the reticle mark 113D and the reference mark 114D is reflected by the half prism 101R, and then transmitted through the relay lenses 102R and 103R to the CCD type 2D.
The reticle mark 1 is provided on the imaging surface of the three-dimensional imaging device 104R.
An image of 13D and the reference mark 114D is formed. The image pickup signal of the image pickup device 104R is transmitted to the reticle alignment device 31.
And the reticle alignment device 31 processes the image signal to calculate the amount of displacement in the X and Y directions of the projected image of the reticle mark 113D with respect to the reference mark 114D.

Similarly, on the half prism 101L side on which the other illumination light ILL enters, the relay lens 102L,
103L and an image sensor 104L are provided, and an image signal of the image signal 104L is also supplied to the reticle alignment device 31.
The amount of displacement of the 3H projection image in the X and Y directions is calculated. In this example, the half prisms 101R and 101L, the relay lenses 102R and 103R, the relay lens 102
L, 103L and the imaging elements 104R, 104L constitute the alignment system 30. Then, reticle mark 113 with respect to reference marks 114D and 114H.
The positional deviation amounts of the projected images D and 113H are supplied to the main controller 7 in FIG.

In the reticle alignment of this embodiment,
"Fine mode" to measure the amount of misalignment with high accuracy when replacing the reticle, or when the reticle is misaligned due to thermal deformation due to irradiation of illumination light, etc. A "quick mode" for checking the position of the reticle is provided.
The alignment in the quick mode is also called “interval alignment”. In the former fine mode, FIG.
After the positional deviation of the image of the pair of reticle marks 113D and 113H is measured in the state shown in FIG. 9, the reference mark member FM and the reticle R are moved in synchronization with each other in the Y direction at the projection magnification ratio. Other three pairs of fiducial marks 114
C, reticle mark images 113CP, 113GP to 113AP, 113E for 114G to 114A, 114E
The displacement amount of P is measured. And the main control device 7
From the positional deviation amounts of these four pairs of reticle marks, the offset, the rotation angle, the distortion, the angular deviation in the scanning direction, and the like of the positional deviation amount of the projected image of the reticle R with respect to the reference mark member FM, and thus the wafer stage 22, are calculated.
The stage control device 1 is designed to minimize the displacement.
3, the position of the reticle R is corrected, the image forming characteristic of the projection optical system PL is corrected so as to minimize the distortion, and the scanning direction of the reticle R at the time of scanning exposure is corrected.

On the other hand, in the latter quick mode, as shown in FIG. 8, only the two-dimensional positional shift amounts of the images of the reticle marks 113D and 113H with respect to the pair of reference marks 114D and 114H are measured. Only the offset and the rotation angle of the reticle R obtained from are corrected. By using this quick mode, alignment of the amount of misalignment of the reticle R can be performed in a short time such as when exchanging a wafer, so that sufficient alignment performance can be maintained without lowering the throughput of the exposure process. it can. Note that these alignment operations are
This is described in more detail in JP-A-7-176468.

At the time of the alignment of the reticle R, the baseline amount of the alignment sensor 28 on the wafer side in FIG. 1 is also measured. That is, in FIG. 9, a reference mark (not shown) for a wafer is also formed on the reference mark member FM in a predetermined positional relationship with respect to the reference marks 114D, 114H and the like.
When measuring the position shift amount of the reticle mark via 0, the base line amount of the alignment sensor 28 is measured by measuring the position shift amount of the reference mark for the wafer via the alignment sensor 28.

Next, an example of the configuration of the transmittance measuring system of the projection optical system PL of this embodiment and an example of the transmittance measuring operation will be described with reference to FIGS. In this example, when the reticle R is aligned in the above-described quick mode, the transmittance of the projection optical system PL with respect to the illumination light IL is measured at the same time. When the reticle R is loaded,
The transmittance of the projection optical system PL includes the transmittance of the illumination optical system after the reticle R and the integrator sensor 9 (beam splitter 8). Further, since the quick mode is a part of the fine mode, the transmittance of the projection optical system PL can be naturally measured even when performing alignment in the fine mode.

In this case, the light quantity (pulse energy) of the illumination light IL incident on the projection optical system PL can be measured from the detection signal of the integrator sensor 9 in FIG. Then, as shown in FIG. 9, the reference marks 114D and 114H used in the quick mode on the reference mark member FM to measure the amount of the illumination light IL transmitted through the projection optical system PL.
A window 105 formed of a pinhole-shaped opening pattern is formed in the light-shielding film therebetween. In the quick mode (interval alignment), the reference marks 114D,
Since 114H falls within the exposure region 16, the window 105 between them is also irradiated with the illumination light IL.

FIG. 10 shows a measuring system for measuring the amount of light passing through the window 105 on the reference mark member FM. In FIG. Inside, it becomes a parallel light beam via the lens 106. After being reflected by the mirror 107, the parallel light flux passes through the lenses 108 and 109 to become a parallel light flux again and is incident on one end of the optical fiber 110. The other end of the optical fiber 110 is installed at a position distant from the main body of the projection exposure apparatus, and the illumination light emitted from the other end is transmitted to the photoelectric detector 1
The light is condensed at 12, and the detection signal of the photoelectric detector 112 is supplied to a transmittance calculator 1b in the exposure controller 1. Since the photoelectric detector 112 is located at a position distant from the wafer stage, the influence of heat generated by the photoelectric detector 112 does not affect the wafer stage. The window 105 and the photoelectric detector 112 correspond to the first detector or the photodetector of the present invention, and the window 105 corresponds to the light receiving surface of the first detector (photodetector). .

An exposure controller 1a for controlling the exposure is also provided in the exposure controller 1, and the detection signal of the integrator sensor 9 of FIG. 1 is supplied to the exposure controller 1a and the transmittance calculator 1b. ing. The exposure controller 1a is also supplied with information on the scanning speed of the wafer stage from the main controller 7. In this example, for example, a value obtained by dividing the detection signal of the photoelectric detector 112 by the detection signal of the integrator sensor 9 according to the transmittance of the projection optical system PL measured using an illuminometer or the like at the time of assembly adjustment is calculated. A conversion coefficient for conversion into transmittance is obtained, and the conversion coefficient is stored in the transmittance calculator 1b. Then, for example, when performing alignment in the quick mode, the transmittance calculation unit 1b
The detection signal of the photoelectric detector 112 is transmitted to the integrator sensor 9.
The actual transmittance of the projection optical system PL is updated by multiplying a value obtained by dividing the detection signal by the detected conversion coefficient by the stored conversion coefficient, and the updated transmittance is used as an exposure amount calculation unit 1a.
To supply.

The exposure calculating section 1b calculates the illuminance on the wafer W from the calculated transmittance and a predetermined conversion coefficient (the transmittance is 100%, the detection signal of the integrator sensor 9 when the transmittance is 100%). Is multiplied by the detection signal of the integrator sensor 9 to obtain the projection optical system P.
The actual illuminance (pulse energy density per unit time in this example) in the exposure area L is calculated, and this illuminance is a predetermined target according to the scanning speed, the width of the exposure area 16 in the scanning direction, the resist sensitivity, and the like. The output of the excimer laser light source 2 of FIG. 1 and the operation of the switching device 6 are controlled so as to be maintained at the values. Thus, even when the transmittance of the projection optical system PL gradually changes due to the use of the ArF excimer laser light, a target exposure amount is always obtained at each point on the wafer W.

In this example, since the measurement system from the lens 106 to the photoelectric detector 112 also passes ArF excimer laser light, when a large light beam is received, the transmittance is reduced due to, for example, volatilization of foreign matter or adhesion of a cloudy substance. May change over time. In order to avoid this, in this example, the small amount of illumination light passing through the pinhole-shaped window 105 is further enlarged to reduce the amount of light per unit area. Further, the time for measuring the transmittance of the projection optical system PL, in this example, for example, the time for measuring the amount of positional deviation of the reticle mark in the quick mode is shortened as much as possible, so that the amount of change in the transmittance in the measurement system is extremely small. It is kept small.

In FIG. 1, when the wafer W is small, the reticle R
The fluctuation of the transmittance of the projection optical system PL can be tracked only by measuring the amount of light transmitted through the projection optical system PL at the same time as performing the alignment. However, since the exposure time becomes longer as the size of the wafer W increases, the amount of change in the transmittance of the projection optical system PL that occurs during exposure per wafer may not be negligible. In such a case, the relationship (irradiation history) between the transmittance variation amount of the projection optical system and the irradiation amount of the illumination light is measured in advance and stored in the exposure amount control unit 1a, and the measurement is performed in accordance with the irradiation history. It is desirable to correct the transmittance multiplied by the detection signal of the integrator sensor 9 by the open loop method.

When calculating the amount of change in the transmittance of the projection optical system PL, the illuminance of the illumination light can be considered to be substantially constant.
(Map). FIG.
(A) shows the projection optical system PL as a function of the irradiation time t.
FIG. 11 is a plot of the transmittance CT of FIG.
In (a), the dotted curve C1 represents the actual variation, and the solid curve C2 represents the predicted variation stored in advance. When the measurement reproducibility at the time of measurement in advance is poor, or when the reproducibility of the transmittance fluctuation is poor, the two curves C1 and C2 gradually separate from each other.

However, in this example, since the transmittance CT is updated each time alignment is performed in the quick mode, for example, the difference between the actual transmittance and the predicted transmittance becomes smaller. That is, FIG. 11B shows the transmittance CP of the projection optical system PL almost regularly in the quick mode in this example.
11 is plotted with the transmittance CT as a function of the irradiation time t. In FIG. 11B, the dotted curve C1 represents the actual amount of change, and the solid line C3 is the curve shown in FIG. Transmittance C corrected for curve C2 in (a)
It represents the variation of T. In this case, time points t1, t2,
.., T5, the transmittance CT of the projection optical system PL is measured, and the curve C in FIG.
A curve obtained by adding a drift component that gradually shifts to step 2 is a polygonal line C3. As described above, by performing the transmittance measurement substantially regularly, the accuracy of the transmittance prediction is increased even between the measurement times.

Further, it is desirable that the interval of the substantially regular transmittance measurement be changed in accordance with the shape of the curve C1 representing the actual transmittance CT. That is, in a section where the amount of change of the curve C1 is large, such as near the time point t4, for example, the transmittance is measured (updated) at short intervals every time one wafer is replaced, and the curve C1 is changed as shown near the time point t1. In a section where the amount of change is small, for example, the transmittance is measured (updated) at a long interval every time two wafers are exchanged, thereby suppressing a decrease in throughput.

Further, as shown in FIG.
D, 114H, etc., or the projection optical system P
When measuring the transmittance of L, a method of using detection light different from illumination light for exposure may be considered. However, if the detection light for measuring the transmittance or the like and the illumination light for exposure are different, the numerical aperture of the detection light (and, consequently, the σ value which is a coherence factor) and the illumination light for exposure are different. Numerical aperture (σ
Value), the measured transmittance or the like may be different from the value under the illumination light for exposure. In addition, there is a problem that the numerical aperture of the measurement system for measuring the transmittance or the like is insufficient. On the other hand, according to this example, the illumination light IL for exposure is used.
Is used as it is as the detection light, so that the amount of displacement of the mark to be measured and the transmittance of the projection optical system PL can be measured with high accuracy.

In order to change the illuminance according to the transmittance of the projection optical system PL as described above, in addition to controlling the output (pulse energy) and oscillation frequency of the excimer laser light source 2, the oscillation frequency, and the light amount variable mechanism, etc. Alternatively, the width of the exposure area 16 of the projection optical system PL in the scanning direction (the width of the fixed blind of the illumination field stop system 11) or the scanning speed of the wafer W may be changed. That is, at least one of the power (pulse energy) of the illumination light IL on the wafer W, the pulse oscillation frequency, the width of the exposure region 16 in the scanning direction, and the scanning speed of the wafer W may be adjusted.

In FIG. 10, the pinhole-shaped window 105 is moved at each position in the X direction so as to cross the exposure area of the projection optical system PL in the Y direction, and the detection signals of the photoelectric detector 112 are integrated. By doing so, the integrated exposure amount at each point on the wafer W can be predicted. By changing the shape of the fixed blind of the illumination field stop system 11 so that the integrated exposure amount becomes constant at each point, a change in the transmittance of the projection optical system PL caused by the irradiation of the illumination light IL is obtained. Illumination unevenness can be corrected.

Further, main controller 7 determines the amount of displacement of the reticle mark image detected via reticle-side alignment system 30 and reticle alignment device 31 in FIG. 8 and the contrast of the reticle mark image. Thus, it is possible to detect the amount of change in the imaging characteristics due to the change in the transmittance of the projection optical system PL. Then, main controller 7 controls imaging characteristic correcting device 51 in FIG. 2 so as to cancel the detected change amount of the imaging characteristic, so that the imaging characteristic of projection optical system PL is kept in a constant state. Can be maintained. The imaging characteristics of the projection optical system PL that can be detected in this example are:
It is at least one of magnification error, distortion, focal position, astigmatism, coma, field curvature, and spherical aberration.
The change in the focal position and the curvature of field can also be adjusted by controlling the height and the inclination angle of the sample table 21 (wafer W) by the focus / tilt control device 27.

The off-axis type alignment sensor 28 of the above-described embodiment is of the image pickup type (FIA type). In addition, a slit-shaped laser beam and a dot array-shaped wafer mark are relatively scanned. Laser
A step alignment (LSA) method or a method of irradiating a diffraction grating wafer mark with two coherent light beams and based on the phase of interference light consisting of a pair of diffracted lights generated in the same direction from the wafer mark. Alternatively, an alignment sensor such as a two-beam interference method (LIA method) that performs position detection by using a method may be used. In the above embodiment, the projection optical system P
The optical system in L is driven to correct the imaging characteristics. Instead, the image is formed using a variable mechanism of the gas pressure between predetermined lenses in the projection optical system PL or a variable temperature mechanism. The characteristics may be corrected.

In the above embodiment, the shape of the illumination area 15 on the reticle R is rectangular, but the present invention can be applied to the case where the illumination area is arc-shaped. However, when the shape of the illumination area 15 is a rectangle almost inscribed in the effective illumination visual field as in the present example, the pattern area of the reticle R is also rectangular, so that there is an advantage that the scanning amount of the reticle R can be reduced. Further, in the above-described embodiment, the present invention is applied to the projection exposure apparatus of the step-and-scan method, but the present invention is not limited to such a scanning exposure type, but the reticle and the wafer are stationary. The present invention can also be applied to a stepper type projection exposure apparatus that performs exposure in a state. Further, the projection optical system PL
Is not limited to the catadioptric type, but may be a refractive or reflective optical system.

Further, in the above-described embodiment, as an example, a detecting operation for detecting the positional relationship between the reticle mark on the reticle R and the reference mark on the reference mark member FM by the alignment system 30 via the projection optical system PL. at the same time,
The transmittance of the projection optical system PL is measured. However, the present invention can be applied to a case other than the alignment system 30 as long as an optical sensor that performs various measurements using the illumination light IL is used. For example,
JP-A-59-94032 or JP-A-8-837
As disclosed in Japanese Patent Application Publication No. 53-53, while irradiating the mark on the reticle with illumination light for exposure, the image of the mark projected by the projection optical system is transmitted through an opening pattern arranged on the wafer stage. The present invention can be applied to a case where a pattern detection system for detecting with a photoelectric detector is used.
When this pattern detection system is used, the window 105 shown in FIG. 9 may be provided near the opening pattern of the pattern detection system. When this pattern detection system is used, the focal position, projection magnification, distortion, astigmatism, field curvature, and the like of the projection optical system can be obtained.

Further, by exposing the pattern image of the reticle R to each shot area on the wafer W while controlling the exposure amount so as to cancel the fluctuation amount of the transmittance of the projection optical system PL as described above, The exposure step for the wafer W is completed. In order to finally manufacture a semiconductor device from the wafer W, a step of performing a function / performance design, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material,
An exposure step of transferring a reticle pattern onto a wafer using the projection exposure apparatus of the above-described embodiment, a device assembly step (including a dicing step, a bonding step, and a package step), and an inspection step are required.

As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention.

[0103]

According to the projection exposure method of the present invention, the transmittance of the projection optical system can be measured almost at the same time as, for example, performing alignment and measuring the imaging characteristics of the projection optical system. Therefore, for example, by measuring the transmittance during the exposure process, there is an advantage that the transmittance of the projection optical system during the exposure process, or the variation thereof, can be accurately monitored.

Further, by controlling the integrated light amount on the substrate based on the calculated transmittance, it is possible to prevent deterioration of the control accuracy of the exposure amount due to illuminance fluctuation (or pulse energy fluctuation) on the substrate. . Next, according to the first to fourth projection exposure apparatuses of the present invention, the projection exposure method of the present invention can be implemented. Furthermore, according to the first projection exposure apparatus of the present invention,
For example, since the transmittance of the projection optical system can be measured almost simultaneously with the alignment of the mask, there is an advantage that the amount of change in the transmittance of the projection optical system during the exposure step can be accurately monitored with almost no reduction in throughput. . By controlling the illuminance and the like of the exposure energy beam in accordance with the variation of the transmittance, the control accuracy of the exposure amount is improved.

In addition, at least one of the projection magnification, the focal position, and the Seidel's five aberrations of the projected image of the mask pattern can be measured based on the detection result of the alignment sensor under the exposure energy beam. By using the imaging characteristic correction mechanism to offset the fluctuation amount, good imaging characteristics can be maintained. Further, the second aspect of the present invention
According to the projection exposure apparatus, for example, the amount of light passing through the projection optical system can be measured almost simultaneously with the alignment of the mask, and the exposure amount can be controlled based on the measurement result. There is an advantage that it is possible to prevent deterioration of the control accuracy of the exposure amount due to the illuminance fluctuation (or pulse energy fluctuation) on the substrate that occurs.

In these cases, the exposure energy beam is pulsed light having a wavelength of 200 nm or less. The exposure energy beam includes a mask stage for moving the mask. When scanning synchronously with respect to
The effect of the present invention is great because the effect of the transmittance fluctuation of the projection optical system, which is particularly large, can be measured or corrected with respect to the pulse light of 00 nm or less.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a projection exposure apparatus according to the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a projection optical system PL in FIG.

FIG. 3 is an explanatory diagram showing a relationship between an illumination area and an exposure area of the projection optical system PL of FIG. 2, and a modified example of the exposure area.

FIG. 4 is a partial cross-sectional view showing a configuration of an off-axis type alignment sensor 28 in FIG.

FIG. 5 is a partial sectional view showing a configuration of a multi-point AF sensor 26 in FIG.

FIG. 6 is a plan view showing the relationship between the laser interferometer on the wafer side in FIG. 1 and the projection optical system.

7A is a side view of the sample stage 21 of FIG. 6 viewed in the + X direction, and FIG. 7B is a perspective view showing a three-axis laser beam incident on the movable mirror 24mY.

8 is a side view showing the configuration of an alignment system 30 on the reticle side in FIG.

FIG. 9 is an enlarged plan view illustrating a relationship between a projected image of a reticle mark and a reference mark.

FIG. 10 is a partially cut-away configuration diagram illustrating a configuration of a measurement system of a transmitted light amount of a projection optical system PL according to an example of an embodiment of the present invention.

FIG. 11A is a diagram showing a relationship between an irradiation time and a predicted value of the transmittance when the transmittance measurement of the projection optical system is not performed periodically, and FIG. It is a figure which shows the relationship between the irradiation time at the time of performing a transmittance measurement, and the estimated value of the transmittance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure control apparatus, 2 ... Excimer laser light source, 5 ... Switching revolver for illumination system aperture stop, 7 ... Main controller, 9
... Integrator sensor, 11 ... Illumination field stop system, R ...
Reticle, PL: Projection optical system, W: Wafer, 13: Stage controller, 17: Reticle stage, 21: Sample table, FM: Reference mark member, 22: Wafer stage, 2
5 ... column, 26 ... multi-point AF sensor (autofocus sensor), 27 ... focus / tilt control device, 28
... Alignment sensor on wafer side, 29 ... Wafer alignment device, 30 ... Alignment system on reticle side, 31
... Reticle alignment device, 41 ... First objective part, 4
2, 44, 47, 53 ... lens barrel, 43 ... optical axis turning part,
46: optical axis deflecting unit, 49: correction optical system, 51: imaging characteristic correction device, 52: second objective unit, 104R, 104L: imaging element, 105: window unit, 112: photoelectric detector, 113A
P to 113EP: reticle mark image, 114A to 114
H: fiducial mark

Claims (14)

[Claims] 1. A projection exposure method for irradiating a mask with illumination light and exposing a substrate with the illumination light via a projection optical system, wherein a measurement pattern arranged on a stage on which the substrate is placed is provided. When irradiating the illumination light, the irradiation area of the illumination light is limited to a predetermined area including a light receiving unit of a photodetector and the measurement pattern arranged in a predetermined positional relationship with the measurement pattern, and the irradiation is performed. A projection exposure method comprising calculating a transmittance of the projection optical system based on an output of the photodetector. 2. The projection according to claim 1, wherein an energy amount of the illumination light incident on the projection optical system at the time of the irradiation is measured, and the measured energy amount is used for calculating the transmittance. Exposure method. 3. An integrated light amount of the illumination light on the substrate is controlled to an appropriate value based on the calculated transmittance and an energy amount of the illumination light incident on the mask. The projection exposure method according to claim 2. 4. A method for transferring a pattern formed on the mask onto the substrate, wherein the mask and the substrate are synchronously moved, and the integrated light amount is controlled to the appropriate value. Adjusting at least one of an energy amount of the illumination light, an oscillation frequency of the illumination light, a width of an illumination area of the illumination light in a moving direction of the substrate, and a moving speed of the substrate. The projection exposure method according to claim 3, wherein 5. An irradiation system for irradiating a pattern formed on a mask with an exposure energy beam having an ultraviolet wavelength, a projection optical system for projecting an image of the mask pattern on a substrate, and positioning of the substrate. A substrate stage to perform;
A projection exposure apparatus comprising: an incident energy amount measuring system that measures an incident energy amount with respect to the projection optical system; a plurality of reference marks corresponding to a plurality of alignment marks formed on the mask; and the exposure. A window for transmitting or reflecting the energy beam is formed and a reference mark member fixed on the substrate stage; a detector for detecting the exposure energy beam passing through the window; An alignment sensor for detecting the amount of displacement between the mark and the corresponding reference mark, the measurement result of the incident energy measurement system, and the projection optical system for the exposure energy beam based on the detection result of the detector And a calculation system for calculating the transmittance of the projection exposure apparatus. 6. An irradiation system for irradiating a pattern formed on a mask with an exposure energy beam having an ultraviolet wavelength, a projection optical system for projecting an image of the mask pattern on a substrate, and positioning of the substrate. A substrate stage to perform;
A plurality of reference marks corresponding to a plurality of alignment marks formed on the mask, and a window portion for transmitting or reflecting the exposure energy beam is formed on the substrate stage. A reference mark member fixed to the detector, a detector for detecting the exposure energy beam passing through the window, and an alignment for detecting a positional shift amount between the alignment mark on the mask and the corresponding reference mark. A sensor, and an exposure control system that controls an exposure amount of the exposure energy beam irradiated onto the substrate from the irradiation system via the projection optical system according to a detection result of the detector. A projection exposure apparatus. 7. The exposure energy beam has a wavelength of 20.
0 nm or less pulsed light, comprising a mask stage for moving the mask, and performing synchronous scanning of the mask and the substrate relative to the projection optical system via the substrate stage and the mask stage during exposure. 7. The projection exposure apparatus according to claim 5, wherein: 8. A projection exposure apparatus, comprising: an illumination optical system that irradiates a mask with illumination light; and a projection optical system that projects the illumination light onto a substrate. A pattern detection system that receives the illumination light via a projection optical system, and a first detector that receives a part of the illumination light that has passed through the projection optical system when the measurement pattern is irradiated with the illumination light. And wherein the transmittance of the projection optical system is determined based on the output of the first detector. 9. A stage disposed on an image plane side of the projection optical system for relatively moving the substrate with respect to the projection optical system, wherein a light receiving surface of the first detector is placed on the stage. 9. The projection exposure apparatus according to claim 8, wherein the projection exposure apparatus is arranged in a position where 10. The projection exposure apparatus according to claim 9, wherein the measurement pattern is provided on the stage, and the illumination light is applied to the measurement pattern through the projection optical system. 11. A projection optical system based on an output of the second detector for receiving a part of the illumination light incident on the mask through the illumination optical system, and an output of the first and second detectors. The projection exposure apparatus according to any one of claims 8 to 10, further comprising: a calculator for determining a transmittance of the system. 12. A controller for controlling an integrated light amount of the illumination light on the substrate to an appropriate exposure amount based on the determined transmittance and an output of the second detector. The projection exposure apparatus according to claim 11, wherein: 13. A projection exposure apparatus comprising: an illumination optical system that irradiates illumination light onto a mask; and a projection optical system that projects the illumination light onto a substrate, wherein the projection exposure apparatus is arranged on an image plane side of the projection optical system. A stage, a measurement pattern provided on the stage, and the measurement pattern is irradiated on the measurement pattern on the stage to detect a part of the illumination light simultaneously with the irradiation of the illumination light on the measurement pattern. A light detector in which a light receiving unit is arranged in an irradiation area of the illumination light. 14. The light receiving unit is a window through which the illumination light passes, and the photodetector is a transmission optical system disposed between the window and a light receiving element on which the illumination light enters. 14. The projection exposure apparatus according to claim 13, comprising: